How to left join tables in LINQ TO SQL to get associated records - sql

Question

I have a linq to sql statement where I am doing join with a bunch of tables , but I need to left join a table as we are not sure if there be any associated records.
We are left joing as we are not sure if every purchase will have a file associated.
Purchase Join - Invc
Purchase Join - FileStore FileStore##Entity
select * from Purchase p
join Invc i on i.Invc_ID = p.Invc_ID
left join FileStore##Entity fe on p.Purchase_ID = fe.Entity_ID
left join FileStore fs on fs.FileStore_ID = fe.FileStore_ID
where p.Purchase_ID = 53
My current linq to sql works for the regular join , how can I left join the file store and store entity table
PurchaseEntity purchase = (from p in TransactionalDbContext.Purchase
join i in TransactionalDbContext.Invc
on p.InvcId equals i.InvcId
where d.Purchase_Id == id
select new DisputeEntity
{
Purchase_Id = p.Purchase_Id,
InvcId = i.InvcId,
SubmittedDate = d.SubmitDt,
InvcNum = i.InvcNum
// get the file elements by left join file
}).FirstOrDefault();

Answer 1

You can easily perform left or right joins by playing with the DefaultIfEmpy method.
Following your example:
from p in dbContext.Purchases
join i in dbContext.Invc on p.InvcId equals i.InvcId
join fe in dbContext.FileStoreEntities.DefaultIfEmpty() on p.Purchase_ID equals fe.Entity_ID
join fs in dbContext.FileStores.DefaultIfEmpty() on fe.FileStore_ID equals fs.FileStore_ID